Development of a conceptual design methodology focused on solar aircrafts

Abstract

This work presents the studies to associated solar aircraft project. Characteristics of existing solar aircraft, their history and developments and associated technical challenges, as well as their limitations and potential use fields have been surveyed. Development related to solar aircraft and low-speed aircraft have been researched and existing aircraft has been investigated, in order to allow an understanding of these aircraft in a comparative and evolutionary perspective. Studies of low-speed aircraft have been performed, in order to check and validate these tools. Examples of new sun-powered designs are also presented. It was possible to observe some semblance of the solar aircraft, in terms of wing loading, with pioneering aviation aircraft from about the years 1890 to 1910. For purposes of analyzing the already-flown solar aircraft, and designing new solar aircraft, the initial study focused in identifying and understanding the differences from these aircraft to conventional aircraft. Several dedicated tools have been developed to, at first, analyze the existing aircraft, and after that, to support the new aircraft designs. Procedures and methods devoted to the estimation of drag, thrust and performance of low-speed, propeller-driven aircraft have been developed. And air vehicles - solar or not - with known performance characteristics have been considered to validate these processes. From this, specific methods for the analysis of solar propulsion processes were developed: Definition of solar irradiation model; definition of propulsive chain, from solar cells to the propeller, and with or without use of batteries. Other methodologies specific to solar aircraft were investigated and defined: a general formulation for obtaining the maximum feasible wing loading for a solar aircraft; aerodynamic characteristics of Reynolds numbers below 150,000; and metrics for estimating the mass of a solar aircraft. With this group of tools, it has been possible to develop two complementary methods for defining a configuration of the solar aircraft from the mission requirements: the Solar Aircraft Design and the Mission Analysis Method. The second one is only required on missions involving large variations in altitude. With the tools developed three concepts of solar aircraft are calculated and presented each one for a specific use. In summary, through this work a general scenario on solar aircraft is developed, aiming the project of solar aircraft; and several perspectives and possibilities for continuation or next steps are pointed out.